Deep-sea megabenthos of the Eurasian Central Arctic based on image analysis.

Photographic surveys were carried out during the expedition ARK-XXVII/3 in summer 2012 (2 August-29 September) in the Nansen and Amundsen Basins for the first time in deep-sea areas previously fully covered by ice. Seafloor was photographed using a towed Ocean Floor Observation System (OFOS). Nine stations separated from each other by 52–689 nautical miles distance (one transect per station) were performed: four in the Nansen Basin (1,2,3,9) at depths 3571–4066 m, and five in the Amundsen Basin (4,5,6,7,8) at depths 4041–4384 m. Stations 1–5 were situated closer to the marginal ice zone and were characterized by first-year sea ice, whereas stations 7–9 were situated at some distance from the ice edge and were characterized by multiyear ice. Station 6 was somewhat closer to the ice edge in 2012 than in any previous year. Total analysed area of the seafloor comprised 16190 m2. Length of transects varied from 210 m to 5500 m.Agassiz trawl samples (frame width 3m, mesh size 2cm) were taken in the immediate vicinity of the photographic transects to obtain specimens for verification of taxonomic identifications based on images.All images were analysed and stored using the image analysis program and database BIIGLE (Bio-Image Indexing, Graphic Labelling, and Exploration) web-2.0 (www.BIIGLE.de). All taxa were labelled in BIIGLE by species/feature name selected from a drop-down list. Visible megafauna was counted and identified to the lowest possible taxonomic level. Taxonomic identifications were made with the assistance of zoological experts. Laser points were automatically enhanced by BIIGLE software, and used for calculation of the seafloor surface area on images in an automated way using a BIIGLE subroutine.